Due to the nature of online dating, not everyone is going to respond. They may not check their messages regularly, they may not have time to send a quality response, or they may not be interested.
Free members can read messages that they receive and can respond by sending an emotigram if they aren't ready to purchase a subscription at that time.
To give yourself the best possible chances of receiving a response when you contact someone, make sure that your profile is complete & up to date. This means that all areas of your profile (including your photos, narratives, interview, temperament, and favorites) are filled in and that the information provided is recent.
In your initial message, make sure that you are as personal as possible. Communication should always include personalized text (i.e. no emotigrams without adding a note), prove that you read their profile by mentioning something that stuck out to you, and provides an easy place for them to respond by asking a meaningful question.
Make sure to contact several members each week to give yourself the best possible chances of being successful on CatholicMatch. This way, if someone doesn't respond, you haven't wasted any valuable time waiting.